Juniper SSG-20-SB Datasheet download pdf (Page 5)

APPLICATION NOTE - Configuring the CX111 for the SSG Series

Power over Ethernet

When available, Power over Ethernet (PoE) can be used to power the bridge. In the event that the bridge is connected

through a switch or a gateway that does not support PoE, an external power supply can be used (provided with the

basic install kit).

When PoE is used, the device will require 4 W to 10 W of power depending on how many modems are connected, so

plan the power budget accordingly.

Dial Modes

The CX111 can be configured in two modes, “always on” or “dial on-demand.” In the “always on” mode, the bridge

connects to the 3G network after booting. The connection is always maintained, as long as there are no network or

connectivity problems.

In “dial on-demand” mode, the bridge will only initiate a connection when it receives traffic from the interface

connecting the bridge and gateway. In particular, DHCP request messages will trigger a connection. Similarly, the

connection will be dropped after a configurable inactivity timeout. The configuration is found under the Modem-

>Settings tab.

Figure 2: Dial modes

Regardless of the mode, the bridge can accept multiple cards simultaneously. In the event of a failure or inability

to connect, the remaining card(s) will be used. The connection priority is user configurable through the bridge’s

management interface.

Deployment Scenarios

In the following section, we will discuss several common deployment scenarios and provide the associated configurations.

CX111 Used for Primary Connectivity

This first scenario shows the gateway configuration when the 3G network is used as the primary WAN link. On Juniper

Networks SRX Series Services Gateways and SSG Series Secure Services Gateways, this can be achieved using the

default configuration by simply connecting the bridge to the ethernet0/0 interface.

Figure 3: 3G network as the primary link

192.168.1.0/24

Trust Zone

CX111

SSG Series

OFFICE

INTERNET

Primary Access

CX111 used as the primary link.

The SSG Series obtains a public address through DHCP.

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Juniper SSG-20-SB Datasheet Page 5